DESCRIPTION: Annexins are a family of structurally related proteins that bind phospholipids in a Ca-dependent manner. They have been implicated in the transduction of mitogenic signals, vesicle fusion and secretion, membrane aggregation, are substrates for important kinases, and have been reported to form ion channels. But their exact biological function has not been determined But even so annexins have a number of properties that make them a nearly ideal system for studying membrane protein interactions. A high-resolution x-ray structure is available. They can be expressed in large quantity in recombinant bacteria. Many interesting mutants have been constructed. Important aspects of their biochemistry are well understood, and their structure can be studied at high resolution by both x-ray crystallography and spin-resonance methods. The objective of this proposal is to bridge the gap between structure and function by studying the effects of annexins on a series of three conductance probes in lipid bilayers. These studies will provide us with basic information on the important topic of membrane protein interaction, suggest possible roles for annexin in vivo and allow for correlation of structure and membrane properties. This project is focused on biophysical aspects of the interaction of the annexin XII protein with planar lipid membranes. The specific aims are: 1. Determine how annexin XII alters the conductance behavior of three different conductance probes: nonactin, tetraphenyl borate, and alamethicin. 2. Determin the topography and oligomerization state of annexin. 3. Investigate the channel-forming abilities of annexin.